The present disclosure relates to a power receiving unit that wirelessly receives power from a power feeding unit, a power receiving control method used in such a power receiving unit, and a feed system and an electronic apparatus that use such a power receiving unit.
In recent years, a feed system performing wireless power feeding (also called wireless power transfer, contact free, or non-contact power feeding) on consumer electronics devices (CE devices) such as mobile phones and portable music players has attracted attention. In such a feed system, for example, a mobile phone (a power receiving unit) may be charged when the mobile phone is placed on a feeding tray (a power feeding unit). In other words, in such a feed system, the power feeding is allowed to be performed without connecting the power feeding unit and the power receiving unit by a cable or the like.
Examples of the method of performing such wireless power feeding may include, for example, an electromagnetic induction method and a magnetic field resonance method (also called magnetic resonance method) using resonance phenomenon. In these methods, power is transmitted with use of magnetic coupling between a power feeding coil of a power feeding unit and a power receiving coil of a power receiving unit. Among them, as compared with the electromagnetic induction method, advantageously, the magnetic field resonance method is allowed to transmit power even if the power feeding unit and the power receiving unit are away from each other, and feeding efficiency in the magnetic field resonance method does not particularly drop even if positioning between the power feeding unit and the power receiving unit is insufficient.
In such a feed system, power is supplied from the power feeding unit to the power receiving unit frequently depending on a load state as viewed from the power receiving unit. For example, in Japanese Unexamined Patent Application Publication No. 2012-085426, a power feeding unit and a feed system that perform power transmission with use of a magnetic field are disclosed. The power feeding unit and the feed system devise proper power supply corresponding to various loads. Moreover, for example, in Japanese Unexamined Patent Application Publication No. 2013-102664, a power feeding unit and a feed system that perform power transmission with use of a magnetic field or an electric field are disclosed. The power feeding unit and the feed system devise proper control irrespective of a load state.